1. Field of the Invention
The system and method of the present invention relates generally to computer digital storage systems, and in particular to computer systems using a plurality of disk drives.
2. Description of the Related Technology
Personal computers have gained substantial popularity among individual users for both business and home use. Personal computers are now being utilized for jobs heretofore performed by mainframe computers and minicomputers. The rapidly growing popularity in the use of personal computers may, in part, be attributed to the substantial improvement in both its speed of operation and its memory capacity of both random access memory (RAM) and disk.
Applications such as transaction-processing which have a high rate of random requests for small amounts of data, or large simulations requiring massive amounts of data that are in excess of the main memory capacity require memory storage capacity only available by using disk storage technology. Mass production of disk systems for personal computers have created low cost and high performance disks having data storage capacities of a hundred megabytes or more. Where a greater disk memory capacity is required, a number of these disks may be used.
Present disk drive technology has integrated the drive electronics ("IDE") in with the drive itself, as in the Conner drive, type CP3204. However, the IDE drive was also intended to be software compatible with existing disk drive controllers such as the WD-1003 manufactured by Western Digital Corporation. Originally, the WD-1003 architecture disk drive controllers were designed to support two disk drives without IDE. IDE drives were adapted so that two could be used. This adaptation requires that both IDE drives monitor the task file register set in each controller, but only allows the drive selected by the drive bit in the SDH (select drive head) register to respond to read requests and to interpret commands.
This adaptation achieves compatibility with the WD-1003 type controller, however, it wastes IDE disk performance. Potential performance is lost because there are two disk drive controllers integral with the two IDE drives but only one controller may be used at a time. This limitation is mandated in order to maintain compatibility with existing disk controller system standards.
The prior art solved the limitation of only being able to access one drive at a time by utilizing a fifty pin connector on an Intelligent Disk Array ("IDA") controller card and by connecting ten wires in the cable going from the IDA controller to each IDE drive. Connection of ten wires connected to pins 31 through 40 and connection of ten wires to pins 41 through 50 of the IDE connector made it unique for each drive. This method has the disadvantage of increasing the costs associated with the connector and cable, and, most importantly, it uses up precious space on the IDA controller card.